If you remove the Expr, you get something that kind of looks like Lisp.
Yes, if you remove a few elements you get (+ a (* b c) 1), as I said a few messages back, which is lisp code and is also lisp data. So you can treat code as data!
You can of course parse code in any language and treat it as data (and it may resemble lisp code!) but it’s not quite the same thing.
Why wouldn't anyone want to write code like this: